Re: [Vala] string <-> bytes conversion in Vala



On Wed, Dec 29, 2010 at 3:51 PM, Anatol Pomozov
<anatol pomozov gmail com> wrote:
Hi

On Thu, Dec 23, 2010 at 12:37 AM, Anatol Pomozov
<anatol pomozov gmail com> wrote:
Hi,

I manipulate with strings in my application such as storing/reading
to/from binary files. And I need to convert a string to/from array of
bytes. What is the best way of doing it in Vala?

Looking into string class http://valadoc.org/glib-2.0/string.html I
see a method called string#to_utf8() that converts string to array of
chars. But I cannot find any other methods.

So I have 2 questions:
 - How to convert a string to array of chars in encoding different
from UTF8. Something like this one
http://download.oracle.com/javase/6/docs/api/java/lang/String.html#getBytes(java.nio.charset.Charset)
 - How to convert array of chars/uint8 back to string? Like this one
http://download.oracle.com/javase/6/docs/api/java/lang/String.html#String(byte[],
java.nio.charset.Charset)

I think I found a way to convert string to bytes in Vala. Actually it
is as simple as casting string to char* and back. Under the hood
strings in vala is just a pointer to char.

Here is an example that shows it:

 string hello = "abcd";
 char* ch = (char*) hello;
 stdout.printf("%c\n", ch[1]); // Second char, that is 'b'

It actually produces an interesting effect. You *can* change content
of a string (that are claimed as immutable)

  string hello = "abcd";
  char* ch = (char*) hello;
  ch[0] = 'z';
  stdout.printf(hello); // Prints 'zbcd'

PS Casting string to/from char* is an interesting technique and worth
mention about it in the tutorial.



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